1. Field of the Invention
The present invention relates to bandgap voltage generators, and in particular, to bandgap voltage generators using metal oxide semiconductor (MOS) devices.
2. Description of the Related Art
Bandgap voltage generator circuits are well known in the art and can be implemented using many circuit topologies. As is well known, the circuit relies on two transistors (generally implemented as two groups of mutually interconnected transistors) running at different emitter current densities, with the current-rich transistor typically running at ten or more times the density of the current-lean transistor. Such a factor of ten or more will cause a 60-millivolt difference between the base-emitter voltages Veb of the two transistors/groups. This difference voltage is then typically amplified by a corresponding factor of ten or more and added to another base-emitter voltage. The total of these two voltages add up to approximately 1.22 volts, which is approximately the bandgap of silicon.
Present bandgap voltage generators now typically use MOS devices as part of a larger MOS circuit. However, as is well known, many implementations of MOS devices result in the creation of parasitic bipolar junction transistors which can produce undesirable parasitic effects, such as circuit latchup or parasitic capacitance which affects circuit startup and operation.